package demo1;

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        TreeNode treeNode = new TreeNode();
        TreeNode.Node root = treeNode.createTree();
        List<Integer> list = new ArrayList<>();
        list.add(null);
        List<Integer> add = new ArrayList<>();
        add.addAll(list);
        System.out.println(add.toString());
    }
}
